Optimal control of freeway corridors

Hierarchical traffic control that adapts to exogenous changes, optimizes system performance, and reduces local disturbances is one of the most effective advanced traffic management system methods for relieving congestion in freeway corridors. Optimal ramp‐metering control lies at the center of such a hierarchical control system. However, current ramp‐metering control strategies are not truly dynamic, are not optimal, or consider only parts of the freeway corridor. This paper presents an optimal ramp‐metering control method to alleviate congestion in the interacting corridor components, including freeway, parallel arterials, and connecting streets. The control formulation employs a continuum traffic‐flow model of the corridor dynamics, and the conjugate gradient method to search for optimal ramp‐metering rates according to the total travel time in the corridor. A test of the optimal metering for a simple one‐ramp segment of a freeway corridor is presented.